How to change the MIDI channel of the interface

After not using the Synvoiz for a while I was wondering why there was no sound coming out of the box. The envelopes didn’t trigger by the MIDI notes. So I checked the channel in my DAW, the cable and counter-checked with another synth. The interface of the Synvoiz wasn’t reacting to any MIDI notes at all. Ok then – lets set the default channel again!

To do this you have to open up the box. Mind that the power cable coming from the PSU-board (which is fixed on the ground of the box) isn’t very long. You will see this:

First view of the Synvoiz when opening the box.
On the left you can see the separate filter-board sitting on the main platine. On the right is the little MIDI-interface-PCB.

Changing the MIDI-channel is pretty straight forward. You have to press a button inside the box and the next MIDI-message going into the interface sets the channel. So just play a note on the right channel – done. But where is this little button?

In fact you have to move the board up to see him. Look here:

Enlarged view of the MIDI-channel-set-button.
Right to the “GND” label on the main PCB you can see a little black button.

That’s it!

New site added – visual overview of the synth

There is a new site added to the main menu which might help some users to get a clue how the Synvoiz works. It’s an interactive image map – hover over a button or potentiometer and read whats going on with this thing. The inspiration comes from the u-he website, where I saw a nice overview over their plugin “Satin” – look here! There are tools to achieve something like this but either they need a lot of JavaScript to work or are ugly to work with. I found this nice tutorial which helped to do the same just with some simple HTML and CSS. At the end it needed a lot time – the Synvoiz has over 100 elements which need explanation! The integration into the WordPress system isn’t elegant but it works. I hope some of you might find that useful.

Happy New Year!

How to tune the Synvoiz

As with guitars the oscillators of the Synvoiz will change their tuning from day-to-day. It should become a habit to tune them before you start working. When I made my first steps into modular synthesizers with a Doepfer A-100 I never cared about tuning the oscillators and wondered later how strange it sounded combined with other harmonic elements in a mix. If you already learned a musical instrument you should be aware of this topic – I never had that pleasure.

The good news is: beside the loosing of the tuning after one day the relation between the two oscillators stays the same. So when you once set them right, you just need to turn the mastertune knob to get back where you were. But one step after another.

Depending of the surrounding setup in your studio you need some kind of reference. This could be an outboard measurement gear like a guitar tuner, a frequency generator/counter or, if you go directly into your DAW with the Synvoiz, a plugin. No matter what you use don’t hesitate to compare the tools. There are several free plugins available on the internet. I like GTune by Graham Yeadon. For Mac this might be another good one. Although they all bypass the audio it should be noted that the one from Waves isn’t bit accurate which means the plugin introduce strange quantization noise.


Mind that you probably have to change your current patch if you go out to your tuner from the audio out. Filter settings with high resonance will interfere with your attempts to tune the synth. Also some tuners like the plugin from Waves have trouble with sinus like sound sources.

Beside the normal audio output of the unit you can use the square wave output (SQ). By doing so you exclude any further pitfalls.

I would tune the second oscillator by ear depending of what amount of phasing between them you like. No need for reservation – with all the prerouted amplitude and frequency modulation and syncing options many interesting sounds build up on a “wrong” tuned second osc. Experiment!

When you change the octave range of your midi notes it is worth to check the tuning again. You will find out that not every note is in the right pitch. Welcome to the analog world!


Analog soul and the CV attenuators

One reason why analog synthesizers are so popular in these modern days in my opinion is the fact that they don’t work every time like expected or surprise you in a way like a VST instrument won’t. Attenuators (or potentiometer also called) for example work in a mechanical way. In consequence every unit acts a little bit different and will change their behavior over time regardless the high industrialized production quality. You can easily realize that by using the Main Tune knob: it has a midway indent which isn’t precise enough to land on the same frequency again once you turned it. In my humble opinion this indent makes not much sense on this pot but since you have three additional knobs to tune the two oscillators it isn’t a problem at all. There are eight attenuators with midway indent altogether used in the Synvoiz and some of them can influence the sound while sitting in their neutral position because of these little imperfections. The best illustration I found so far is the CV 1 pot at the filter section. Default the LFO 1 is routed there. I recorded a standing bass sound with no modulation dialed in – CV 1 in center position.

While recording this I turned the LFO 1 frequency slowly up and you can hear that very clear in a change of harmonic content. The solution for this is pretty simple.  Just plug a spare cable into the CV 1 socket. Now the sounds stays stable:

As long as the source of prerouted modulation is only slowly changing in time the variations in sound might appeal to most users. If you have trouble to understand a certain aspect of your sound and suspect an ongoing “secret” modulation just plug a cable into the according socket to bypass the routing.

Starting position

You got the unit, turn it on, connect the audio and midi cable and don’t hear anything while pressing keys on your keyboard? Here are some first hints to get started:

There are four locations where the output volume can be influenced. The master volume doesn’t need any explanation – just turn it on. At the envelope section (the faders) you will find in the top left corner one called BIAS which basically bypasses the whole VCA section. The fader underneath called CV controls the envelope amount going into the VCA. In the filter section you have two input controls. For the start tune only the IN 1 into middle position*. Now comes the tricky part – the extra VCA section in the middle of the oscillators. When the MIX control is in middle position and the little black knobs around it are all turned counterclockwise you should hear nothing. The MIX control blends in OSC 1 or 2. If you want to hear both at the same time use the BIAS controls over it. Now you should hear something. Turn the knobs listen whats happening and try out some stuff. Happy tweaking!

* The filter input can be overdriven pretty easily. The IN 2 is the ring modulated signal of both VCAs.

Computer noise

First to make things clear: The Synvoiz has an excellent signal-to-noise ratio. I don’t have calibrated measurement utilities but can tell you that the unit is silent when it needs to be. Compared to other analog or digital synthesizers it’s in the same ballpark.

Not so my lovely Retroverb. It’s a spring reverb and open to a lot of influences beside the input signal. Additionally it has a muffled sound so you tend to grab an equalizer and push those higher frequencies. Doing this last week I heard a noise which I know to good from bad wiring in cheap recording setups. Today’s CPUs change their power needs thousand times a second dependent on the load it is given. Even with modern plugins you won’t stress out your CPU to the max so it has idle times where it tries to save power (and heat emission). So it is likely that this emits to your audio cabling in some way. Here is an example of the Retroverb’s noisefloor with the interfering noise of the CPU:

It’s easy to exclude other sources by giving the CPU something heavy to do like the Prime95 tool. With the software running the noise floor of the unit sounds like this:

Please mind that the sound examples are heavily equalized so it’s clear what I am talking about.

The troubleshooting started. Replacing the audio cables didn’t help. Also I realized that it’s not input dependent which means the interfering noise comes from within the unit. Changing position of the PSU also didn’t get me any further but moving the whole unit removed the unpleasant sound. After switching off unit by unit nearby the Retroverb I found the culprit: The power supply cord of the TFT! At the beginning of my investigation I thought about the PSU of the computer or that of the Retroverb itself – which isn’t a standard DC one so not so easy to replace (12 v AC). After superseding the old cord with a new one the noise floor isn’t as polluted as before but you still hear it:

With a proper gain staging the noise is on a level I can live with for the moment as there is no better place for the Retroverb in my small room.

By the way when I activate the filter of the unit the signal-to-noise ratio is immediately reduced and the computer noise only barely noticeable. Filters tend to emit noise that’s the reason why in every synthesizer the filter comes before the VCA.


First contact

Finally! With a lot of excitement I unpack the wonderful produced wooden case.

Notice the plug for the power supply: a mini XLR!